InterviewSolution
Saved Bookmarks
InterviewSolution
| 1. |
(a) A certain buffer solution contains equal concentration of X− and HX. The Kb for X− is 10-10. What is the pH of the buffer?(b) Assuming that the buffer in blood is CO2 −HCO3−, calculate the ratio of conjugate base to acid necessary to maintain blood at its proper pH, 7.4.Ka of H2CO3 = 4.5 × 10-7 . |
|
Answer» (a) Given, Kb = 10−10 pKb = − log[Kb ] = −log[10−10] = 10 log 10 = 10 \(\because\) pKa + pKb = 14 or pKa = 14 - pKb = 14 - 10 = 4 For acidic buffer, pH = pKa + log\(\frac{[Salt]}{[acid]}\) \(\because\) [X−] = [HX] \(\therefore\) pH = pKa = 4 (b) Given, pH = 7.4 Ka = 4.5 × 10−7 CO2 + H2O ⇌ H+ + HCO3− Ka = \(\frac{[H^+][HCO_3^-]}{[CO_2]}\) Now pH = - log [H+] Or [H+] = 10−pH = 10−7.4 = 4.0 × 10−8 So, from equation (i), \(\frac{[HCO_3^-]}{[CO_2]}\) = \(\frac{K_a}{[H^+]}\) \(\frac{4.5\times10^{-7}}{4.0\times10^{-8}}\) = 11 |
|